First of all, whats the difference between /48 and /64, i can see that /48 is shorter...

Basically a /48 lets you easily subnet out multiple /64 allocations for your network.So for example, if you are operating a router with multiple interfaces for different LANs on your network, you can allocate a /64 per LAN out of your larger /48 allocation to each interface.

As mentioned in other threads: rDNS for the /64 used for the tunnel's point-to-point connection is not delegated to you, only rDNS for the routed /64 and /48 allocations.In this case your routed /64 is "1f0b" not "1f0a".